Liquid level responsive device



Nov. 4, 1941.. a, E. EWE RTZ 2,261,495

LIQUID LEVEL REsPONsIvE DEVIFGE Filed April 14, 1939 L Q \QJ Q v v Q a sN .z Q 5% g, 3

Patented Nov. 4, 1941 UNITED STATES PATENT" OFFICE LIQUID LEVELBESPONSIVE DEVICE Gordon E. Ewertz, Elizabeth, N. J. Application April14, 1939, Serial No. 267,947 6 Claims. (or. 177-311) This inventionrelates broadly toa liquid level responsive device, and particularly toan electrically actuated device for gauging the contents of a tankcontaining two or more fluids having different electrical resistances.

It is a wellknown fact that it is prohibitive to use any device inconnection with a tank containing hydrocarbons or other dangerousliquids if said device causes a measurable electric current to fiow insaid tank. Under certain circumstances it is even prohibitive toutilizean electrically actuated device in connection with a tankcontaining water.

The primary object of this invention is to provide a liquid levelresponsive device for fluid containers, as, for example, water in tanks,or, a liquid supporting other non-mixing'liquids, as, for example, waterand oil, or, other fluids having difierent electrical resistances.

Another object of the invention is to provide an apparatus that may belocally and/or remotely operated and observed, and that makes possible asafe and accurate measuring of a liquid, as, for example, a hydrocarbon.

As it is well known in the electrical art that a small change of inputvoltage to a vacuum tube amplifier results in a large change of poweroutput from said amplifier, and that electrical devices may be operatedby the change of input voltage, it is an object of this invention toutilize such a structure in the apparatus of this invene tion and at thesame time limit the possible flow of current in a tank to a value sosmall that hazards caused by electrolysis and sparking are eliminated.

The invention consists of a liquid level responsive device as set forthin the following specification and particularly as pointed out, in theclaims.

The figure of the drawing is a diagrammatical illustration of a liquidlevel responsive device embodying my invention and as applied to a tankcontaining water and a hydrocarbon.

In the drawing, I represents a closed container,

as, for example, a fuel tank of a hard tank fuel system wherein water 2supports a hydrocarbon 3 in a manner well known to those skilled in theart. Obviously the tank may contain other fluids having differentelectrical resistances, as, for example, water and air, and the tank maybe open or closed as circumstances demand. Mounted within the tank I area plurality of electrodes 4, 5, 6, I, 8 and 3, all insulated from eachother and from the tank. Any number of electrodes may be provided forthe tank I as may be desired.

As illustrated these electrodes consist of insulated rods of differentlengths exposed to the fluids in the tank at different levels therein,but it is evident that said electrodes may be of any desiredconstruction provided they have contact points embodied therein whichare exposed to the fluids in the tank, are located at difierentelevations in the tank, and are insulated therefrom. The

electrode 4 is common to all the circuits which include the otherelectrodes, and thetank itself may be used as a common lead in place ofthe electrode 4 if it is so desired. The electrodes 5, 6, I, 8 and 3 areconnected by wires H), II, I2, l3 and I4 respectively to terminals I5,I6, l1, l8, and I9 respectively of a selector switch having an arm 2|embodied therein which is arranged to contact with said terminals.

The operating mechanism of the gauge may be located adjacent to the tankI, or at a distance therefrom, and embodies therein an audio-frequencyvacuum tube amplifier 22, well known in the art, and operated from asuitable-source of electric supply. There are several types of vacuumtube amplifiers available, all well known in the art, and in which asmall change of input voltage results in a large change of power output,capable of actuating'lights, bells, relays and other electrical devices,and it is obvious that the type of current provided must be that forwhich the amplifier is designed to operate from. The electric currentfor the amplifier 22 is supplied through wires 23 and 24 connected toterminals 25 and 26 respectively provided upon said amplifier.

The amplifier '22 is provided with input terminals 21 and 28 to whichwires 29 and 3!! respectively of an input circuit are attached. The wire29 is connected to a contact 3| of an adjustable resistor 32; while thewire 30 is connected to the secondary winding of a transformer 33.Included in the input circuit with the adjustable resistor 32 is aresistor 34 connected to the contact 35 of an adjustable resistor 36 inturn connected to the secondary winding of the transformer 33. Thetransformer 33 is excited by a source of alternating current throughwires 31 and 38. It will be evident that the magnitude of the inputvoltage applied to the terminals 21 and 28 is dependent on the positionof the contact 3| on the adjustable resistor 32, the resistance of saidresistor 32, the resistance of the resistor 34, the position of thecontact 35 on the adjustable resistor 36, the resistance of saidresistor 35, and the voltage across the secondary of the transformer 33.

The electrodes 4, 5, i, I, 8 and 3 are connected across the inputcircuit by connecting the electrode i to the input wire 30 by means of awire 353, and by connecting the arm 2! of the selector switch 261' tothe input wire 29 by means of a wire to.

It will be understood that the resistors 32 and 3t may be one and thesame, and of any value.

Also that the adjustable resistor 38 is merely a convenient manner oftaking a reduced voltage from the secondary of the transformer 33 inorder that a commercially available transformer may be used for thetransformer 33. It is also possible to substitute one or more highimpedance choke coils for the resistors 36 and 32, or even for thresistor 38.

The frequency of the input voltage applied to the input of the vacuumtube amplifier 22 may be whatever desired; and the transformer 33 may bereplaced by any source of alternating or direct current. A vacuum tubeoscillator can, for example, be employed in place of the transformer 3%and its output voltage applied through current limiting and voltagereducing means as shown by 3 5, 32 and 3| to the input of the vacuumtube amplifier 22, or, a source of interrupted direct current such as isobtained from a vibrator or any other current interrupting means may besimilarly applied to the input of the vacuum tube amplifier 22 withoutdeparting from the spirit of the invention, as each of these alternateelectrical units mentioned is the equivalent of the of the vacuum tubeamplifier 22 by wires 43 and 44 respectively is an alternating currentrelay 45 which operates a single pole double throw switch 45, the arm ofwhich is connected by a wire 41 to the supply wire 24 for saidamplifier. A contact 48 of the switch 48 is connected by a wire 43 to alamp 50, and a contact 5! of said switch is connected by a wire 52 to alamp 53. The lamps I50 and 53 are connected together by a wire 54, andthe latter is connected by a wire 55 to the supply wire 23 for thevacuum tube ampli fier 22. It will thus be seen that when the relay 45is energized that the lamp 53 will be illuminated and the lamp 53 willbe extinguished, and that when the relay is deenergized that the lamp 53will be illuminated and the lamp 0 will be extinguished. 7

It will be understood that a lamp, bell or any other responsive meansmay be used in place of the relay 45, and that whether the responsivemeans employed is also used for controlling auxiliary devices isimmaterial.

The general operation of the device hereinbefore specifically describedis as follows: Assume first that the arm 2i of the selector switch 20 isin circuit with a contact connected to an electrode that is exposed tothe hydrocarbon 3 in the container 1; that the transformer 33 has asecondary voltage of 3.15 volts at 60 cycles, that the adjustableresistor 33 is, for example, 100 ohms, and that the contact 35 is sopositioned that the voltage is reduced to 0.035 volt. Then if theresistor 34 is 8,000,000 ohms and the adjustable resistor 32 is2,000,000 ohms, the contact 3| may be positioned at a point where therewould be an input voltage of 0.0035 volt applied to the input of thevacuum tube amplifier 22. In this particular instance the amplifier 22is designed to have a sufllcient gain to energize the relay 45, therebycausing the arm 'of the switch 46 to engage the contact 43 and therebyilluminate the lamp 50 with an input voltage of 0.0035 volt to saidamplifier. The hydrocarbon 3 being a nonconductor of electricity therewould be no current flowing in the tank, and the voltage present in thetank would be 0.0035 volt.

Again assuming that the arm 2| of the switch 20 is in circuit with anelectrode exposed to the water in the tank, as is the case with theelectrode B of the drawing, the input voltage to the amplifier 22 willbe reduced due to the shunt action of the water, the amplifier willcease to energ'me the relay 45, the arm of the switch 46 will becomedisengaged from the contact 48 and engage the contact 5! thereby causingthe lamp 50 to be extinguished and the lamp 53 to become illuminated.Thus it can be determined which of the electrodes are exposed to thenon-conducting fluid 3 and which are exposed to the conducting fluid 2.Obviously, the greater the number of levels at which readings can betaken, the finer will be the readings.

The electrodes and the water 2 between them act as a volume control forthe amplifier 22. The input voltage is reduced to a commerciallyunmeasurable value and there is no possible chance for sparking to takeplace. Also, because of the current limiting and voltage reducing meansprovided, the current which flows in the tank circuit is limited to sucha low value that hazards caused by electrolysis are eliminated, and itis impossible to measure the current even with laboratory equipment.This holds true even if the electrodes are changed to contacts and theyare actually closed.

The current limiting and voltage reducing means are very important inthis apparatus. As an example, if the input voltage was taken from anysource, the current that could flow in the tank circuit upon partial orcomplete cross circuit would depend upon. the resistance of the circuitand the current capacity of the input voltage source. Also, unless thissource is loaded by the tank circuit sufllcient to reduce the inputvoltage, the responsive means in the output circuit of the vacuum tubeamplifier 22 will not respond to changes in the tank circuit. Thus notonly is the current limiting and voltage reducing means used to insurethe operation of the responsive meansln the output circuit of theamplifier, but it also eliminates the hazard caused by electrolysis andsparking.

I claim:

1. Liquid .level responsive means having, in combination, anaudio-frequency vacuum tube amplifier, a source of electric potentialtherefor, an input circuit including a source of alternating electriccurrent for said amplifier, current limiting and voltage reducing meansin said input circuit, a container for non-mixing fluids havingdifierent electrical resistances, electrodes in said container exposedto said fluids and connectcd across the input circuit of the amplifierto short circuit said input circuit through the fluid of leastelectrical resistance, and means in the output of the amplifierresponsive to changes of input voltages to said amplifier.

2. Liquid level responsive means having, in combination, anaudio-frequency vacuum tube amplifier, a source of electric potentialtherefor, an input circuit including a source of alternating electriccurrent for said amplifier, current limiting and voltage reducing meansin said input circuit, a'container for non-mixing fluids havingdiflerent electrical resistances, electrodes positioned at differentlevels within said container exposed to said fluids and connected to theinput electric current for said amplifier, current limiting and voltagereducing means in said input circuit, a container for a liquid and atleast one other separate hazardous fluid, said fluids having differentelectrical resistances, electrodes in the container exposed to saidfluids and connected to the input circuit to shunt said circuit throughthe fluid of least electrical resistance,

and means in the output of the amplifier responsive to changes of inputvoltages to said amplifier.

4. Liquid level responsive means having, in

combination, an audio-frequency vacuum tube amplifier, a source ofelectric potentialthereior, an input circuit including a source'ofalternating electric current for said amplifier, current limiting andvoltage reducing means in said input circuit, a container for a liquidand another sepa-' through said conducting fluid when two of saidelectrodes are immersed therein, and means in the output of theamplifier responsive to changes of input voltages to said amplifier.

5. Liquid level responsive means having; in

combination, an audio-frequency vacuum tube amplifier, a source ofelectric potential therefor,

an input circuit including a source of alternating electric current forsaid amplifier, current limiting and voltage reducing means in saidinput circuit, a container for water and a non-mixing hazardous fluid,the latter being a non-conductor or electricity, electrodes positionedat difierent levels within said container exposed to said fluids andconnected across the input circuit of the amplifier to shunt said inputcircuit through said water when two of. said electrodes are immersedtherein, and means in the output of the amplifier responsive to changesof input voltages to said amplifier.

6. Liquid level responsive means having, in combination, anaudio-frequency vacuum tube amplifier, a source of electric potentialtherefor, an input circuit including a source of alternating electriccurrent for said amplifier, current limiting and voltage reducing meansin said input circuit, a container for fluids, means in the containerexposed to said fluids and connected across said input circuit to shortcircuit the latter, and means in the output or the amplifier responsiveto changes or input'voltages to said amplifier.

GORDON E. EWERTZ.

